SelectionChanged event in ComboBox is not fired (Deleted)

I have DataGridTemplateColumn (which contains CellEditingTemplate and CellTemplate) and other column DataGridTextColumn in a DataGrid. ComboBox is embeded in CellEditingTemplate. What I want to do is update value in DataGridTextColumn when SelectedValue
is changed in the ComboBox. So I added event SelectionChanged in the ComboBox. However it seems the event is never fired somehow. I couldn't figure out why.